Removal Of Heavy Metal Lead And Copper From Pickling Waste Liquor

With the rapid development of China's construction,automobile,electric power,machinery and other industries,the demand for steel products has increased year by year.Before the surface coating of steel products,hydrochloric acid is generally used to remove rust on the steel surface,resulting in a large number of pickling waste liquid and bringing in heavy metal ions.The iron-based water treatment agent is one of the acidification waste liquid resource treatment methods,but the problem of heavy metal removal has not been considered in practical applications.In this paper,the feasibility of removal of Pb²⁺and Cu²⁺from pickling waste liquid by iron powder reduction,phosphate method,phosphate and iron powder method were studied.Influencing factors such as pH,reaction temperature,reaction time and dosage were investigated.The reaction conditions were optimized and the best combination schemes were determined.The effects of other heavy metal ions on the removal of Pb²⁺and Cu²⁺by iron powder reduction were also studied.Main results are belowed:?1?When the iron powder reduction method was used to remove Pb²⁺,the main influencing factor was the iron powder dosage,and the secondary influencing factor was the initial pH value.The best combination scheme was:iron powder dosage 50 g/L,initial pH value 1.7,reaction temperature 40°C reaction time 15 min.At this time,Pb²⁺removal rate was 82.4%;When the iron powder reduction method was used to remove Cu²⁺,the main influencing factor was the iron powder dosage,and the secondary influencing factor was the reaction time.The best combination scheme was:iron powder dosage 6g/L,initial pH value 0.9,reaction temperature 30°C,reaction time6min.At this time,the Cu²⁺removal rate was 99.4%.According to the characterization and analysis of the precipitated product,when the iron powder treated the pickling waste liquid,the precipitated product were mainly in the form of lead and copper.?2?Phosphate method and phosphate combined with iron powder method can effectively remove Pb²⁺in pickling waste liquid.When Pb²⁺was removed by phosphate method,the main influencing factor was phosphate dosage.The secondary influencing factor was initial pH.The best combination scheme was:phosphate dosage 50g/L,initial pH 1.7,reaction temperature 40°C,reaction time 45min,at this time,the Pb²⁺removal rate was 82.1%;When the phosphate and the iron powder method were used to remove Pb²⁺,the main influencing factor was m?phosphate?:m?iron powder?,and the secondary influencing factor was reaction time.The best combination scheme was:phosphate:iron powder is 5:2?phosphate dosage 50 g/L,iron powder 20 g/L?,initial pH value 0.5,reaction temperature 40°C,reaction time 15 min,at this time,Pb²⁺removal rate was 92.4%,compared with phosphate alone,the removal rate increased by10.3%.Phosphate reacted with Pb²⁺,and the product exists in the form of lead phosphate precipitates,such as PbHPO₄?Pb₃?PO₄?₂ and Pb₅?PO₄?₃Cl.?3?Phosphate method had a poor effect on Cu²⁺removal in pickling waste liquid,and phosphate combined with iron powder method can achieve better removal effect.When the phosphate method was used to remove Cu²⁺,the main influencing factor was the initial pH value,and the secondary influencing factor was the phosphate dosage.The optimal combination scheme was:phosphate dosage 50g/L,initial pH value 1.1,reaction temperature 50°C.reaction time 30 min.At this time,the Cu²⁺removal rate was 26.7%.When the phosphate and the iron powder method were used to remove Cu²⁺,the main influencing factors was reaction time,and the secondary influencing factors was initial pH value.The combination scheme was:phosphate dosage 40g/L,iron powder 2g/L,initial pH value 1.0,reaction temperature 30°C,reaction time 12min,Cu²⁺removal rate was 97.4%,compared with phosphate alone,the removal rate was increased by 70.7%,.Phosphate reacted with Cu²⁺and iron ions,and the product was present as a coprecipitated form of copper iron phosphate?Cu₃Fe₄?PO₄?₆?.?4?When the effects of other heavy metal ions on the removal of Pb²⁺and Cu²⁺by iron powder reduction were investigated,it was found that Cr³⁺did not interfere with the removal of Pb²⁺by iron powder,while Cu²⁺and Ni²⁺inhibited the removal of Pb²⁺by iron powder and increased with the concentration of interfering ions.The inhibitory effect was enhanced.When the concentration of Cu²⁺and Ni²⁺were 500mg/L,the removal rate of Pb²⁺were decreased by 16.5%and 42.1%.Cr3+slightly inhibited the removal of Cu²⁺by iron powder,and the inhibitory effect gradually increased with the increase of interfering ion concentration.When the concentration of Cr³⁺was 500mg/L,the removal rate of Cu²⁺was decreased by 2.5%,.Pb²⁺and Ni²⁺do not interfere with the removal of Cu²⁺by iron powder.